The present invention relates to generally a urine sensor to be used with an automatic urine disposal system for persons such as bedridden aged, bedridden patient and physically disabled persons for whom it is difficult to control timing of urination and/or to make a disposal of urine after discharged.
It is often difficult for those persons as have been described above to control timing of urination on his or her own will and/or to make disposal of urine after discharged by his or her own ability. In order to overcome the difficulties for such persons, there has already been proposed an automatic urine disposal system comprising a urine receiver to be put against a wearer's crotch around a urethral, suction means such as a suction pump provided separately of the urine receiver adapted to guide the amount of urine collected by the suction means in the urine receiver to a urine reservoir. The suction pump evacuates air within the hermetically sealed urine reservoir to generate a differential pressure between the urine receiver and the urine reservoir so that the differential pressure causes the amount of urine within the urine receiver to be guided into the urine reservoir.
This urine receiver of prior art includes a urine sensor to detect urination and thereupon to activate the suction pump. The urine sensor includes a pair of electrodes and a urination detection circuit adapted to become live and to activate the suction pump when the paired electrodes are electrically connected to each other via urine. The urine receiver of this type, for example, disclosed by Japanese Laid-Open Patent Application No. 2004-267517A comprises a topsheet, a urine absorbent sheet, a urine backflow prevention sheet and a pair of electrodes constituting the urine sensor interposed between the topsheet and the urine backflow prevention sheet. In the case of this urine sensor, the urine backflow prevention sheet functions to prevent backflow of urine from the urine absorbent sheet toward the urine sensor and, even if urine is quickly absorbed by the urine absorbent sheet and still stays thereon, no erroneous signal indicating urination is output on the basis of such urine staying on the urine absorbent sheet.
However, the electrodes used in this urine sensor of prior art have a relatively large area entirely exposed and consequentially the suction pump may erroneously be activated due to a contact between the electrodes and the topsheet on which an amount of urine stays. In addition, depending on a posture of a wearer of the urine receiver, the topsheet may come in contact with the urine sensor and erroneously activate the suction pump.